Apparatus for electrodeposition of metals



May 23, 1933- s. o. cowPER-coLEs 1,910,150

APPARATUS FOR ELECTRODEPOSITION OF METALS I l l I I if. Il

May 23, 1933 s. o. cowPER-coLEs 1,910,150

APPARATUS FOR ELECTRODEPOSITION 0F METALS Filed May 6, 1950 2Sheets-Sheet .2

. ment in the circumferential direction of the.

Patented May 23, 1933 UNITED STATES PATENT OFFICE F. C. METAL PROCESSESLIMITED, OF LONDON, ENGLAND,

A.- BRITISH COMPANY APPARATUS FOR ELECTRODEPOSITION METALS Applicationled May 6, 1930, Serial No. 450,180, and in Great Britain May 15, 1929.

My invention has for its object the rapid and economicalelectro-deposition of metals, especially copper, of a quality superiorto any hitherto attainable and in what I believe to be a new physicalcondition such that the deposited metal is at once and withoutfurthertreatment suitable for the manufacture of a variety of industrialproducts as hereinafter indicated. The metal is of exceptional purity,density and hardness; thus, inthe case of copper, a hardness numeral of130 or more on the Brinell scale and a. breaking stress in tension of 35tons per square inch are obtainable. The process results in uniformityof structure owing to the fact that the metallic crystals are, to alarge extent at least, broken down; any remaining crystals all lie inone direction, thus also conducing to uniformity. The metal may beobtained as sheet, strip or Wire or in the form of cylinders or tubes ofany desired diameter.

According to the invention the cathode employedfor theelectro-deposition of the desired metal is constituted by a horizontalmandrel rotated at a speed resulting in 'turbulence of the electrolytesuiiicient to break up the` film of exhausted electrolyte in proximityto the mandrel, rollers or discs free to revolve and capable of alimited movemandrel being arranged to bear on the metal depositedthereon. The rollers are mounted on a carriage or the like which ismoved to and fro in a direction p-arallel tothe axis of the mandrel, thearrangement preferably roimay be varied by altering the pressure exbeingsuch that the rollers are operative during motion in one direction only.The abovementioned qualities of the metal deposited erted by the rollersor discs or the number of to-and-fro movements performed in unit prior'English specification No..

1898, inthat in the latter case there 1s emtime, or by changing boththese factors.

It will be realized that this invention differs essentially from thatdisclosed in my 21,971 of ployed a vertical mandrel-wholly immersedandrotated at a speed suiiciently high to throw olf by centrifugal forcethe cathodic film of exhausted electrolyte containing hydro,D n bubbles,whereas in the present case the n andrel is only partially immersed andthe speed is merely sufficient to lift, at the point at which therotating surface of the mandrel emerges from the electrolyte, a smallquantity of the electrolyte a few inches above the normal surface of theliquid, from which height it falls back giving the appearance of acascade, producing agitation of the liquid and breaking up the cathodicfilm. The fact of the rollers being operative during axial travel in onedirection only results in equality of treatment over the whole surfaceof the mandrel and causes the metal ,to

be deposited in such a manner that any crystals which in the process arenot broken down lie substantially in one direction, producing uniformityin the metallic structure hitherto, I believe, unattained. The rollersare preferably so mountedas to bear on the mandrel solely by their ownweight, such pressure determining to a large extent the density andother 'qualities of the deposlted metal; in order to vary the pressurerollers of different weights are preferably employed, but obviously suchvariation may be secured by means of spring pressure or weights appliedto the frame or the like carrying the rollers.

In describing my invention I w1ll take copper as the metal to bedeposited from a suitable electrolyte such per and in the first place Iwill describe the process as adapted for the manufacture of coppersheet. In a suitable vessel contaming the electrolyte I mount therotatable mandrel, so that about half of the circumference of themandrel is below the surface of the electrolyte. Below the mandrel Iplace the anode which may consist of copper bars placed i continuoussemi-cylindrical conductor adjacent to and following the contour of thecylindrical surface of the mandrel, the space between the cathode andanode being about one quarter of an inch. The mandrel consists of acylinder or drum whlch may be wholly or partly made of metal, but whichas sulphate of copside by side so as to form a treated in any knownmanner to prevent the adhesion of the deposited metal. A special methodof treating the surface to prevent adhesion forms a subsidiary featureof my present invention. Suitable arrangements are made for rapidlyrotating the mandrel at the critical speed above referred to, which,however, is not so high-I that any substantial part of the li uid iscarried up and over the drum, but s cient to cause the turbulence in theelectrolyte necessary to break up the cathodic film as above described.

Bearing upon that portion of the mandrel which is not immersed in theelectrolyte there are arranged revoluble rollers or discs of metal orglass or any other suitable material. In copper deposition I have founda very suitable material is a high-percentage ferro-silicon alloy Awhichis not attacked by copper sulphate solution. The rollers or y discs areso arranged that they exert a comparatively hea pressure per unit areaof contact on the eposited metal owing to the fact that that area isvery small. In practice I have found it desirable to deposit a thinlayer of copper before allowing the rollers or discs to be applied. Therollers or discs are free to rotate by frictional contact with thesurface of the mandrel, (it being understood that in this term I includethe metal deposited there0n,) and are also capable of a limited movementin the circumfer? cntial direction of the mandrel: I refer to themaccordingly as floating rollers. Further, they are arranged and mountedso that they can be moved in contact with the mandrel transversely inv adirection parallel its axis. The transverse movement of the rollersordiscs is a reciprocating movement, but they should only contact withthe mandrel when moved in on'e direction; the return -movement should beout of contact therewith. Thefunction of these rollers or discs is (l)still further to ensure the film of electrolyte on the mandrel beingbroken up and (2) at .the Sametime through their rolling pressure andrubbing action, due to the transverse motion, to produce a deposit of'copper which'possesses an extraordinary degree of toughness.. Theconsolidating effect of the rollers or-discsalso assists in eliminatingany nodules or roughness which the deposited copper may tend to form,with the result that Athe latter presents throughout an unusually smoothand even surface.

One or more-rows of rollers or discs may be iitted -to bear upon themandrel and in the case of long thin mandrels which have a tendency tosag I may lind it expedient to arrange a row of rollers or discsunderneath the mandrel and two rows on the top. In order to prevent thedeposition of metallic excrescences at the edges of the mandrel ess, Iplace secondary electrodes at both ends of the mandrel. These secondaryelectrodes are semi-circular plates made of lead or other inertelectrical conductors, or of wood, vulcanite or other insulatingmaterial or a combination of an insulating and conducting materialcapable of withstanding the electrolyte, so arranged that they are inclose proximity to the mandrel and preferably provided with a flange tooverlap a portion of its depositing surface. The effect of thesesecondary electrodes is that they reduce the rate of deposit at theextreme ends of the mandrel and instead of the metal building up at theends, the deposit can be so regulated that the ends are just as smoothand the thickness of the deposited metal the same as on the other partsof the mandrel, or it can be arranged so that the deposit slightlytapers off. Again a medium applied to facilitate stripping or to othercauses, I may find it desirable, after deposition for a comparativelyshort time and, before application of the floating rollers or discs, tocause a rapidly revolving brush to travel over the surface of themandrel, whereby the thin deposit is levelled up and further depositisfree from iaws and blemishes. Preferably the mandrel is provided with atransverse groove or an insertion of a material of higher specificresistance than that on the mandrel surfaceas a whole, with the resultthat the deposit is locally thinner or even entirely absent, therebyfurnishing a line along which stripping of the deposited sheet from themandrel may'be started.

Metal sheet produced in this way is so homogeneous and smooth that it iscapable of being advantageously used for prmtlng plates or gramophonediscs or other purposes for which electro-deposited copper 1s notnormally'adapted.

The process of electro-deposltlon have described is applicable to theproduction of tubes or cylinders. In the deposition of metal in the formofseamless tubes greater difficulty is sometimes experienced indetaching the tube from the mandrel than in the case where the removalofthe deposited metal 1s effected by stripping it off from: the mandrelas a sheet or strip.. I have foundthat 1n order to ensure the readydetachment of a tubular deposit it is advantageous to use copper orbrass-coated mandrels which have their surfaces highly polished and arethen coated With a solution containing 0.05% to 0.5% of beeswaxdissolved in turpentine, to which solution 1% of carbon bisulphide isadded. The same composition may be used, if desired, to facilitate thedetachment of sheets or strips.

In order to obtain a surface on the mandrel which at reasonable costwill ensure that the inner surface of the deposited sheet, (that is thesurface in contact with the mandrel), is perfectly smooth and free fromimperfections, I construct the mandrel or drum of welded steel or ironsheet or cast iron, which is then turned and polished. On this surface Ithen electro-deposit copper, having first made the surface passive `bytreatment with nitric acid or other well-known means so as to ensure theadherence of the copper deposited. Upon a mandrel having a surface soprepared, polished and treatedwith a preparation for facilitatingdetachment I am then able to deposit copper according to the processherein described to produce sheets,

tubes or cylinders whose inner surface is mir-` Vror-llke and whoseouter surface also 1s un` usually smoothl and free from imperfections. Iproduce copper strip or wire having the special characteristicsobtainable in accordance with the present invention in the followingway. I form upon lthe surface of the mandrel a helically disposedV-shaped groove as described in my prior specification No. 21,568 of1904,-the pitch of the helix corresponding with the width of the stripwhich it is desired to produce. The V-shaped groove forms a Weak line ofcleavage in the deposited metal, enabling it to be removed from themandrel in the form of a continuous strip, which may then be rolled ordrawn through draw plates or dies to form wire.

The copper strip as Aunwound from the mandrel has a small iin on'eitheredge due to fission along the line of cleavage in the metal deposited inthe Vshaped groove. Unlessv special means are taken to eliminate thisfin it is apt to result in imperfect wire. I find that the best means toeliminate it is to run the strip in the process of stripping off fromthe mandrel between rollers which are so shaped or are set at such anangle that they press the small fins into the body of the strip so thatwhen it is drawn through a round die there is no fear of the finsturning over and forming lines or imperfections in the finished wire. i

For the purpose of my invention I use any of the electrolytes ordinarilyused for the deposition of the metals to which my invention relates. Ifind, however, that in depositing copper according to my invention anadvantageous electrolyte for certain purposes consists of a strong,almost saturated, solution of the sulphate of aluminium, mag- ,nesium orother alkaline metal, to each gallon instance at 100 amperes or more persquare foot, the voltage at the terminals of the cell being in the orderof 0.8. The solution is preferably Worked hot at a temperature of about90o C. If a copper anode is used in such a solution it dissolves awayevenly leaving a smooth surface.

It will be realized that in the case of all the above describedoperations the anode constitutes the source of the metal which isdeposited on the revolving cathode, the electrolyte merely acting as avehicle for the transfer of this metal. It is, however, possible toemploy the electrolyte as the source of the deposited metal, the anode,if desired, being made of lead, carbon, ferro-silicon or otherelectro-chemically inert material. The possibility is thus afforded ofobtaining by an electrolytic method a metal directly from a compoundcontaining it provided that such process; for example, in order torecover copper from a sulphide ore in this manner I may proceed asfollowsz- The ore is first concentrated by any of the wellfknown methodsand if such method has necessitated the use of oil this must be removedby treatment with a suitable solvent or by applying the necessary heat.The concenti-ated ore is then mixed with a sodiuln chloride solution ofa strength of about 10% and the sludge and the ore from the solution arecirculated through a tank in which, as above described, is a horizontallrevolving cathode andan anode composed of Igraphite or other suitablematerial. The solution with the ore in lsuspension is caused tocirculate in the intervening annular space so that the copper sulphideis attacked by the nascent chlorine and converted into a cuprous copperchloride-the copper being deposited on the revolving cathode. In thisWay lit is found possible to work at 'a very high current density-say,200 amps. per square foot-with a low voltage and, on account ofthesolution ing reducedwith evolution of sulphuretted hydrogen and thesulphur finally recovered.

In the case of an ore containing different metals, it may be possible,by what might be termed fractional electrolyzation, that is to say, byaltering the conditions under which the electrolytic process is carriedout, successively to obtain a deposit of each of the metals in a purestate. For example, in treating a sulphide ore containing nickel 4%,copper 9% and cobalt 2% the ore or concentrate is first roasted in asuitable furnace to a bright red heat with constant stirring until thesulphate state is reached. The roasted ore is leached first with waterand then with 10% sulphuric 4acid solution, the temperature notbeingallowed to rise above 30 C. After the desired extraction has beenobtained, the solution is decanted and contains the copper and cobalt,the nickel remainingin the residue. -The latter is subjected to a1:further leaching operation with 10% sulphuric acid at 90 C. to extractthe nickel and the solution is then electrolyzed in the manner abovedescribed at a temperature of 80 C.; an insoluble anode is used and avoltage applied suilicient to result in a current density of about 60amps. per square foot, whereupon the nickel is deposited as a cylinderwhich may be stripped off in the form of sheet.

The first leaching solution containing the copper and cobalt salts iselectrolyzed at a temperature of 30 C. and current density about 10amps. per square foot with acidity 6% free acid and, using an insolubleanode, the cobalt is deposited on a suitable revolving cathode. When allthe cobalt has been removed another revolving cathode 'is substituted,the current density is raised to 30 amps. per square foot, thetemperature to 60 C. and the acidity to about 940% free acid, whencopper is obtained by deposition on the cathode,vthe iron in solutionbeing crystallized out from time to time.

In all cases I have found it possible to operate economically at ahigher current density than has hitherto been commercially employable;such current density is obtainable by the application of voltagessubstantially lower than those used heretofore, due largely to theeilicient depolarization and continual renewal of the cathodic filmsecured by running the rotating cathode at -the critical speed abovementioned.

The mechanical features of the apparatus required for carrying out myinvention may take various forms. A form" of apparatus which I havefound suitable is one in which the mandrel is supported by means oftrunnions mounted in bearings outsidethe de` positing tank. As current,which is of considerable magnitude, passes from the mandrel or drumthroughwthese bearings I pro-- vide for their being Water-cooled andlubricated by means of graphite or other electrical 5- 'understood andreadily carried into effect it will now be described more fully withreference to the accompanying drawings which illustrate various forms ofapparatus for depositing metal having the uniquequalities attainable inaccordance with the invention,

'and wherein F' res 1 to 3 show respectively in side view, end view andplan apparatus suitable for depositing metal on a mandrel ofcomparatively large diameter with a view to its subsequently beingstripped off inthe form of a sheet.

Figures 4 and 5 respectively illustrate in section two forms of floatingrollers or for bearing on the mandrel,

-Figures 6 and 7 depict an alternative mechanism for producing theto-and-fro transverse movement of the rollers or discs,

Figures 8 and 9`show in section and diagrammatic plan respectivelyapparatus suitable for the manufacture of tubes,

Figures 10 and 11 depict respectively in side view and end view rollerswhereby the fin existing on a strip which has been deposited on thehelically grooved mandrel and subsequently stripped olf may be disposedof, Figures 12 and 13 being respectively sections of the said stripbefore and after treatlnent by the rollers.,

Referring to Figures 1 to 3, the mandrel 1 is mounted within a suitablevat or the like 2, which is preferably lead lined, by means of a shaft 3supported in bearings 4 vertically adjustable by means of screws 5passing through suitably threaded supports 6. As indicated, the'bearings 4 are preferably open-topped to facilitate ready removal andreplacement of the mandrel l'and, on account of the fact that current isfed to the mandrel through the bearings, they are lubricated withgraphite, or other electrically conductive lubricant, being preferably,also in view of the large current to be transmitted, water-cooled bymeans of ducts 7 connected by pipes 8 with a water supply. To relievepressure on the bearings, the mandrel may be made hollow and watertight,so that a portion of its weight Y is taken byflotation in theelectrolyte,the level of which is conveniently about as indicated inFigure 2. The mandrel is rotated by means of a pulley 9, or analogousdriving member, from a counter-shaft 10, which also, by means of wormgearing '11, serves to rotate a cam -shaft 12 the purpose of which willbe hereinafter described. The anode 13 constituted by a copper castingor sheetor, as indicated in Figure 2, by a series of copper bars is inthe form of an arc of a cylinder surrounding the lower portion of themandrel which constitutes the cathode, being Lsupported 'in this iposition by means of cradles or like members vproximity to the endsshown, with inwardly directed flanges of lead yor other inert materialwhich protrude be- .tween the edge of themandrel and the anode 13. Thesecondary electrodes 15 are supportedby means of rods or like members 16which are .attached toy the bearings 4 by means' of adjusting nuts 17;thusthe distance of each secondary electrode from the end of the manyidrel may be varied in order to produce the different effects as regardsthe thickness of the deposit above mentioned It-will be' Vseen that, asthe secondary electrodes are supendwise '35.

`ported.from the bearings 4, they partake in any vertical adjustment ofthe position of the mandrel 1 relatively to the anode 13 which may begiven effect to in order to obtain the desired current density or tocompensate for wastage of the anode 13.

The floating rollers or discs 18 bearing on the mandrel are carried on aspindle 19 supported by two bars 20 adapted to rock on a pivot bar 21but vprevented from moving thereon by collars 22 fixed on the bar. Awiper 23 is also preferably loosely pivotedto the spindle 19 in such aposition as to make contact with the mandrel just before it asses underthe rollers 18 for the purpose o removing any grit, dirt or otherextraneous matter which might have found its way into the electrolytelThe pivot bar 21 is journalled in bearings 24 supported in uprights 25so that it is free to move in an axial direction for the purpose ofproducing the desired transverse travel of the rollers or kdiscs 18across the mandrel 1. To ez'ect this movement the cam shaft 12 isprovided with `a snail cam 26 adapted to co-operate with a roller 27provided on a lever 28 pivoted at 29 and connected by a linkV 30 withthe pivot bar 21; thus rotation of the`cam'26 results in travel of therollers or discs 18 at a uniform rate across the mandrel 1 in adirection from left to right as seen in upon reaching the right-hand endof the ,mandrel the lever 28 together with its assoi rapidly toward theleft by ciated members, is allowed to be drawnback the action of aweight 31 connected with the pivot bar 21 by a cord.or the like 32 33a`s indicated: excefsslve shock due to rapid motion of the lever,- pivotbar and rollers may be prevented by the provision of a suitable springbuffer 34. In order that, on the return stroke, the rollers or discs'18shall be Figure 1, and

passing over a pulley.

out of contafct with the mandrel 1, they are lifted by means of 'asecond cam 35 o erat-A ing through'a lever 36 pivoted at 37 an connected by a link 38, having a double knuckle Joint 39, with a tippingbar 40v supported in arms 41 hinged around the pivot bar 21, the saidtipping bar 40 bearing on the upper side of the rear end of the bars 20.rThe cam 35 is, as indicated, so shaped that during ashort period of itsrevolution the lever 36 is depressed with the result that the rollers ordiscs 18 are raised from contact with the mandrel this action beingtimed to take place synchronously with `the return transverse movementof the rollers or discs. Asindicated, the vat2 is preferably supportedby Ainsulators 42 and suitable means, not shown, are providedl formaking'electrical supply connections respectively with the bearings 4and the anode 13.

In order that the rollers or discs 18 may individuall have freedom notonly to revolve but o movement in the circumferential direction of themandrel, the constructions shown by way of example in Figure 4 orFigure5 may be adopted. Referring to Figure 4, each roller 18 isformed^with a central aperture 43 of a diameter larger than that of thesplndle 19, the rollers vbeing preferably separated by distance-pieces44. According to the construction depicted in Figure 5, the

vspindle 19 is surrounded by a bush 45 free to revolve thereon and thespaces enclosed within the apertures 43 in the discs 18 and the bush arelled with sponge rubberr46 whereby the desired freedom of movement ofthe individual rollers is permitted.

Y In the alternative form of transverse travel mechanism showniniFigures 6 and 7, the pivot-bar 21 is stationary and the bars 20 arecapable of sliding movement along it. Parallel to and on each side ofthe pivot bar 21 are screwed spindles 47 and 48 which are either rotatedin opposite directions, as de- A scribed'y below, or formed withoppositely handed threads. The bars 20 are provided with half-nuts 49and 50 adapted respective- 'ly to co-operate alternatively with thespin-v dles 47 and 48, the engagement of one half- ',nut or the otherwith itsco-operating spin-v dle being determined by the lie of` apivoted weight 51 adapted to oscillate between pins 52 litted betweenthe bars 20. The spindle 47 is the one whereby the operative transversemovement of the rollers 18 is produced, th' spindle 48 being employedto"efect the return stroke: consequently, it is desirable that thelatter spindle shalll revolve more rapidly than the former. The spindle48 may be driven from the counter-shaft 10 or from any other suitablyplaced shaft by means of a cord or chain 53 passing over a pulley 54 onthe s' indle48. A second pulley 55 on this spin 1e serves 'to drive, bymeans of a cross cord or belt 56, a pulley 57 of larger diameter tted onthe spindle 47. In order to effect reversal at the ends of the forwardand return strokes stationary cam plates 58 are provided to engage thepivoted arm on which the weight 51 is mounted, thereby throwing overthis weight from contact with one of the pins 52 to contact with theother pin and so rocking the bars 20 to disengage the halfnut inoperative relation with one of the screwed spindles and engage the otherhalfnut with its spindle. The bars 20 are preferably provided with acounterweight 59 so that the pressure of the rollers or discs 18 on themandrel 1 is determined wholly or to any desired extent by the weight ofthe rollers themselves.

In the apparatus shown in Figures 8 and 9, two mandrels are employedeach having a corresponding set of floating rollers 18 carried by acommon frame 60 resting on a pivot bar 2l and adapted to be tilted onthe return stroke by means of a tipping` bar 40 as in the'modificationabove described. As, however, in the manufacture of tubes the length ofthe mandrels 1 may be very con siderable, it is possible that saggingmight be produced as a result of the pressure of the rollers 18.Consequently, a supplementary set of floating rollers 61 isprovided onthe underside of the mandrels in order to afford them some degree ofsupport. The set of rollers 61 is supported by means of a rod 62 adaptedto slide vertically through the frame 60 and provided 'with a wing-nutor the like 63 whereby the upward pressure of a spring 64 serving tosupport the rod 62 and rollers 61 may be deposed. In order that, on thereturn stroke, the rollers 18. may be lifted from their respectivemandrels by the tilting of the frame 60, it is obviously `necessary thatthe rollers 61 shall be lowered out of contact with the mandrels 1 andthis result is attained automatically by means of a collar 65 fitted onthe rod 62 and provided with an inclined surface 66 adapted toco-operate with a .similarly shaped surface on a sleeve 67 loose on therod 62 aud bearing against a fixed abutment 68 in such a manner thatrotation of the sleeve 67 results in depression 0f the rollers 61. Thesleeve 67 is provided with an outwardly projecting rod 69 which, on theforward or operative stroke of the rollers 18 and 61, occupies theposition relatively to the frame 60 shown in full lines in Figure 9.' Onapproaching the end of the operative stroke however, the rod 69encounters a stop pin 70 and thereby, on account of the continuedtransverse travel of the frame 60, the rod 69 is retarded and brought tothe position shown in dotted lines so rotating the sleeve 67 anddepressing the rollers 61. The tippingbar 40 then operates to tilt theframe 60 and the reversing mechanism comes into action to perform thereturn stroke, whereupon the rod 69 on approaching the end of thatstroke 'encounters a second stop pin, not shown, which-restores it toits original full-line position, thereby allowing the spring 64 to raisethe rollers 61 into contact with the mandrels 1 at/the same moment asthe tipping b ar 40 is operated to allow the rollers 18 to bear on themandrels.

The apparatus for removal of the fins ywhich essentially exist on astrip or w1re produced by depositing metal as above on a helicallygrooved mandrel and subsequently stripping it olf, depicted in Figures10 and 11, comprisesessenti'ally two rollers 71 and 72, the former. ofwhich is provided with a. rectangular groove to accommodate that side'of the strip or wire on which the fins. do not exist, that is to say,the lower portion of the wire a section of which before treatment isshown in Figure 12. The second roller 72 is formed with a groove, thebottom ofwhich `is bevelled, as indicated at 73 in Figure 11, so thatwire of a section 'shown in Figure 12 when passed between the rollershas its section altered to that depicted in Figure 13. The outline ofthe original section is indicated in Figure 11 in dotted lines and itwill be seen that between that portion of the upper surface of the wireintermediate of the fins and the opposing bottom of the groove in theroller 72 there is a space, this being provided to enable the fins to besqueezed by the bevelled portions 73 of the groove into the body of thewire rather than folded over on the outside thereof. The result is thatthe above mentioned intermediate surface of the wire is forced outwardsto lill the space above referred to as that the section of the Wire, asillustrated in Figure 13, corresponds with the space between the rollers72 and 73 constituted by the respective grooves in these rollers. Itwillbe realized that instead of employing a single roller 72, tworollers set at an'angie andl adapted to operate one on each lin may beemployed, the peripheries of the rollers being shaped so that theircombined action in co-operation with the roller 71 in disposing of thefins is similar to that above described.

While the process and apparatus have been described more particularly intheir application to the production of copper sheet, tubes, strip orwire, the invention is also applicable to the deposition of other metalssuch, for example as zinc, nickel, cobalt or silver, whether from theirores or other compounds as above indicated or by transfer from an anodeof the metal in question.

lVhat I claim and desire to secure by Letters Patentof the United Statesis 1. Apparatus for the electrosdeposition of metal comprising a vat forcontainingthe electrolyte, an anode immersed therein and a cathode inthe form of'a rotating mandrel on which rollers, free to revolve andcapable of a limited movement in the circumferential ment of the rollersis comparatively slow in one direction followed by a rapid returnmovement.

3. Apparatus as in claim 1, wherein the transverse to and fro motion ofthe rollers is produced by cam-and-lever mechanism.

4. Apparatus. as in claim 1, wherein the transverse to and fro motion ofthe rollers is produced by reversing screw mechanism.

5. Apparatus as in claim 1 in which camand-lever mechanism is providedfor lifting the rollers out of contact with themandrel during theirtransverse motion in one direction.

6. Apparatus as in claim 1, in which the rotating mandrel is providedwith a shaft mounted in bearings located outside the vat and verticallyadjustable by such means as a screw.

7. Apparatus as in claim 1, wherein the rollers are supported by a frameconstituted by bars transverse to the axis of the mandrel and carried bya pivot bar about which it may rock and which permits of its transversemovement across the mandrel and the frame is extended on the side of thepivot bar remote from the rollers and is adapted to co-operate with atipping bar whereby, on the return transverse stroke, the rollers areaisled from contact with the rotating man- 8. In apparatus as in claim1, means'for permitting the circumferential movement of the rollersaccording to which they are mounted on a common spindle which passesthrough an aperture in each roller substantially larger in diameter thanthat of the spindle.

9. In apparatus as in claim 1, means for permitting the circumferentialmovement of the rollers according to which they are mounted on a commonspindle surrounded by a bush free to revolve, the spindle and bushpassing through an aperture in each roller of substantially greaterdiameter than the external diameter of the bush and filled veithresilient material such as sponge rub 10. Apparatus as in claim 1, inwhich a set .of rollers is arranged to bear on the underside of themandrel.

11. Apparatus for the electro-deposition of metal, comprising a vat forcontainingtthe electrolyte, an anode immersed therein, a cathode in theform of a rotating mandrel on the upper surface of which rollers, freeto revolve and capable of a limited movement in the circumferentialdirection of the mandrel, are adapted to bear, a set of rollers arrangedto bear on the underside of the mandrel, means for automaticallylowering the set of rollers bearing on the underside of the mandrel andsubsequently raising the rollers bearing on the upper side of themandrel, and a common frame capable of transverse motion for supportingthe rollers bearing on the upper side of the rotating vmandrel and thosebearing on the underside thereof.

12. Apparatus as in claim 11, wherein a spindle supporting the rollersbearing on the underside of the mandrel is provided with a collar havinga cam surface adapted to co-operate with a corresponding surface on amember which is automatically moved as each end of the transverse strokeis approached, whereby the spindle is depressed and the rollers loweredout of contact with the mandrel.

SHERARD OSBORN COWPER-COLES.

